Introduction and Type of Glue
In this step, we will be rejoining the two prepared half-blanks together, and it is essential to use the right type of glue. The glue should have specific properties such as:
- Water-resistant because during playing, especially the mouth hole and SAC will get wet.
- Strong enough to prevent the flute from breaking, even if it falls on the ground.
- It should provide sufficient drying time to enable adjustment of the halves.
- The seam between the halves should be as invisible as possible to make the flute visually appealing.
I am using “UHU-Wasserfest,” a German brand, but most people prefer to use Titebond II or III, as stated on the resources page. However, I like using UHU glue.
Glueing
To prepare for glueing I wipe all surfaces with Acetone which helps to clean and reduce oily surfaces. Since I am doing this, I haven’t experienced any problems with glue joints that split when turning/rounding the flute later on.
To join the two half-blanks, apply glue to one half while ensuring there are no uncovered areas. It can be challenging to determine the right amount of glue to use. Personally, I use my index finger to spread the glue carefully and judge whether it feels right. With practice, you’ll develop a feel for it.
Next, align both blanks as precisely as possible in all directions, paying particular attention to the perfect circle at the bore end and mouth end. Use your index finger to push against the seam slightly and feel if it’s aligned.
Begin clamping carefully at both ends of the flute. Tightening the clamps may cause the halves to disalign. If this happens, decrease the pressure and re-align the halves until you’re satisfied. Sometimes, the halves may be slightly bent, causing them to align at the start and end but not perfectly at the center. In such cases, add an “alignment” clamp in the middle of the flute in the direction of the misalignment. This will force the two halves to align even better, but be careful not to tighten this clamp too much, as it may hold a slight gap between the halves. Tighten the clamp just enough to ensure that the two walls are aligned.
Add more clamps until there is no space left. Typically, I use around ten clamps, but be careful not to tighten them too much, as this will squeeze all the glue out. Tighten the clamps just enough to hold the pieces and “nearly” close the seam.
After clamping, there will be glue squeezed out inside the mouth hole, SAC, and bore. Use a wooden dowel with damp fabric wrapped around it to clean the bore immediately after clamping. Wipe it inside to remove most of the glue and smear the rest as flat as possible inside the bore. For the mouth hole, use Q-Tips to do the same. Unfortunately, cleaning the SAC seams from inside is challenging, and I haven’t found a good way to do it yet. However, it doesn’t seem to affect the sound as long as the amount of glue used was not excessive.
Let the glue dry with the clamps for 24 hours. If you need to build more flutes, you can remove the clamps after a few hours, but I usually don’t.
